In U.S. Pat. No. 5,901,780, a sorption system configured to operate continuously when the vehicle is not running is disclosed. The system comprises a heat exchanger in the passenger area piped to receive conditioned heat transfer fluid, a sorber cooling system located outside the passenger area and having two sorber beds, each of sufficient capacity to meet the cooling requirements of the passenger compartment for a predetermined interval, and piped to be alternately operated at duty cycle corresponding to the predetermined interval where one bed is absorbing and the other bed is desorbing to drive refrigerant around a refrigerant loop, the refrigerant loop including an evaporator for delivering conditioned heat transfer fluid to the heat exchanger during air conditioning (cooling), a fuel fired heater outside the passenger area and of sufficient thermal capacity to desorb a single sorber bed during the predetermined interval, and one or more valves for directing heat transfer fluid heated by the fuel fired heater. The system operates in a heating mode wherein a heat transfer fluid heated by the fuel fired heater is directed to the heat exchanger, and a cooling mode wherein heat transfer fluid heated by the fuel fired heater is alternately directed to the respective sorber beds for refrigerant absorption and desorption. The sorption system and method of operation disclosed in the aforesaid U.S. Pat. No. 5,901,780 is incorporated herein by reference.